Method of electroplating



Dec. 7, 1954 J. F. BEAVER, JR

METHOD OF ELECTROPLATING Filed Oct. 14, 1949 Gttorneq United StatesPatent METHOD OF ELECTROPLATING John F. Beaver, Jr., Osborn, OhioApplication October 14, 1949, Serial No. 121,394

4Claims. (c1.204-23) This invention relates to electroplating processesand apparatus, and more particularly to a means and method of platingrecessed, hard to plate, objects, although not necessarily limitedthereto.

The electroplating of articles of complicated design, presentingcrevices and other recessed surfaces, ordinarily is not attempted,particularly when a relatively heavy metal deposit is required. This isbecause in conventional plating methods prominent areas of the objectbecome heavily plated while the recessed areas receive little if any ofthe metal deposit.

The object of the invention is to'simplify and improve the method aswell as the means and mode of electroplating recessed objects, wherebysuch objects may not only .be economically manufactured, but will bemore satisfactory, having a better deposit of plate thereon, such platebeing substantially evenly deposited over the surface area of theobject.

A further object of the instant invention is to advance theelectroplating art by bringing objects of complicated design readilywithin the practice of the art.

Another object of the invention is to provide a method of and apparatusfor evenly distributing a metal deposit of any desired thickness over asurface of irregular or complicated design.

A further object of the invention is to provide generally conventionalelectroplating apparatus incorporating an alternatively usable abilityto plate objects having recessed, hard to plate areas.

Still another object of the invention is to present a new method ofelectroplating wherein there may simultaneously be carried out the stepsof removing excess metal from heavily plated areas and of redistributingthe removed metal over more lightly plated areas.

A still further object of the invention is to provide simplifiedapparatus for practicing the foregoing method.

A still further object of the invention is to introduce, and renderpracticable, the principle of bi-polarity of the object being plated.

A further object of the invention is to provide a method and apparatusfor plating objects possessing the advantageous features, the inherentmeritorious characteristics and the mode of operation herein mentioned.

With the above primary and other incidental objects in view as will morefully appear in the specification, the invention intended to beprotected by Letters Patent consists of the features of construct-ion,the parts and combinations thereof, and the mode of operation, ashereinafter described or illustrated in the accompanying drawings, ortheir equivalents. -In carrying out the above and other objects of theinvention, a method of and apparatus for electroplating have beenachieved involving use of one or more auxiliary anodes in the customaryelectroplating system, plus the use of adjustable polarity control meansoperable to produce in a first stage of operation a common polarity inthe main and auxiliary anodes and an opposed polarity in the object andoperable in a second stage to produce opposed polarities in the main andauxiliary anodes and in conjunction therewith to induce a bipolarcondition in the object. In the practice of the invention, therefore,during the first stage of the operation the. object is plated insubstantially the usual manner and as a result prominent areas acquire aheavy metaldepositwhile areas of lesser prominence are lightly coat-Then during the second 'stage of operation someiof the metal previouslydeposited on the promi ed, if at all.

2,696,466 Patented Dec. 7, 1954 nent areas is removed therefrom andredistributed over the recessed areas until both areas are evenlyplated.

Referring to the accompanying drawing, wherein is found the preferredbut obviously not necessarily the only form of embodiment of theinvention,

Fig. 1 is a partly diagrammatic viewvof an electroplating installationelectrically connected in accordance with the first stage of anoperating cycle;

Fig. 2 is a view similar to Fig. 1, showing the parts electricallyconnected according to the second stage of the cycle;

Fig. 3 is a view similar to Fig. 2, showing an alternative connection tothe object in the second stage of operation;

Fig. 4 is a view of an electroplating installation, showing the wiringdiagram for obtaining the results in Figs. l and 2; and

Fig. 5 is a view similar to Fig. 4, showing the wiring diagram embodyingthe alternative connect-ion of Fig. 3.

Like parts are indicated by similar characters of reference throughoutthe several views.

Referring to the drawing, in the practice of the invention apparatus isutilized which includes a tank 10 substantially filled, as indicated,with an electrolytic solution. Immersed in the solution are a main anode11 and one or more auxiliary anodes 12 made of the metal being depositedor any suitable conductor. An object to be plated is indicated at 13 andshown immersed in the solution. The object is an example of hard toplate articles, presenting prominent portions 14 projecting toward themain anode 11 and relatively remote recessed areas or corners 15. Insetting up the apparatus for operation, the auxiliary anodes 12 arelocated in or close to the recessed areas while the main anode is spaced2. conventional distance from the object.

Electrical conductors to connect the anodes and the object to be platedin an electrical circuit are provided, and in accordance with theinstant invention, there is further provided polarity control means forinitiating the successive stages of an electroplating cycle.

For illustrative purposes, the two alternating stage of the cycle areseparately shown in diagrammatic form in Figs. 1 and 2. As shown in Fig.1, in the first stage the main anode 11 and auxiliary anodes 12 are bothconnected to a conductor 16 leading from a suitable source of electricalcurrent and representing the positive side of such current source.Object 13 is connected to a conductor 17 leading from the same currentsource and representing the negative side thereof. According to thefirst stage of operation, therefore, a substantially conventionalelectroplating operation takes place in response to closing of theelectrical circuit.

The elements 11 and 12 function as anodes and the object 13 as thecathode with the result that metal is deposited on the object. The firstoperational stage is continued for a period of time sufficient toproduce a substantial deposit of metal on the prominent surfaces of theobject. Then the circuit is opened, interrupting the plating action, andadjustments of polarity made to condition the apparatus for second stageoperation, as shown in Fig. 2.

According to this arrangement, the main anode 11 is connected tonegative conductor 17, auxiliary anodes 12 remain connected to positiveconductor 16 and object prominent areas is removed and the deposit onthe recessed areas 15 is increased. It is believed that the action WhlChtakes place in this stage is one of redis tributing metal taken from theprominent surfaces and I a deposit of metal on the recessed surfaces. 7

The second operational stage is discontinued after a determined intervaland may be repeated, if necessary, until}. an :evenplating' of desiredthickness; is obtained Aoverthe entire surface of, the object. The-timeof each- In response to closing of the cir-.

stage of the cycle is varied according to plating thickness desired andthe structural detail -of-theobject being plated,

the second or bi-polar stage. being usually of shorter duration, andwith higher voltage, than the first stage.

In some;cases, during the. bi-polar ,stage of the cycle,.,-,

it may; be advantageous. to. connect; the. :object beingplated :througharesistance to the... positive side of the current source.

without, however, altering its cathodic relationship to The resultobtained is to make: the ob.- ject more anodic to the cathode(normalyanodell) auxiliary anodes. 12. Such an arraugementis shownin IFig. 3 wherein a tank 18, main anode 19, auxiliary anode- 21, object 22,positive conductor 23. and negative conductor 24 occupy the samerelationship as the corre-v sponding elements of the embodiment of Figs.1 and-2. .1

In .-this.instance, however, in the second stage of operation, which .isthat shown, the object 22. is connected to positive conductor 23 by alead incorporating a variable resistor 26.

Considering .the .means for changing polarity in .the

Arrangements of this a switch 27. Through these arms positive conductor16.v

is permanently connected to a contact 23 and negative conductor 17is-permanently connected toa contact 29. A lead 31 extends from contact28 tothe auxiliary anodes 12' so that these anodes are continuouslyconnected to the positive side of the current source. Contacts 32 onrespective arms of switch 2'7 are alternatively engageable with a pairof spaced contacts 33 and 3 5 and another pair of spaced contacts and36. Thus the contact 32 on that switch arm which is positive by reasonof-its connection with conductor 16 is alternatively engageable withcontacts 33 and 35. Contact 33 is connected by a lead 37 with the mainanode 11. Contact 35 has no electrical connection. Contact'36 isconnected bya lead 39 with lead 37 and thereby to the main anode 11.

In the operation of the apparatus, the switch 27 normally stands in anupright or neutral position and the electrical circuit is open. Toinitiate the first stage of the electroplating operation, the switch 27is moved from neutral to a position engaging contacts 32 with contacts33 and 34 respectively. A circuit thereby is closed from conductor 16through parallel leads 31 and 37 toanodes 11 and 12, throughtheelectrolytic bath, object 13 and lead 38 back to negative conductor17. the-first stage of operation and initiate the second, switch 27 isreturned to neutral position and its throw in that direction continueduntil the contacts 32 respectively engage contacts 35 and 36. A circuitthen is closed from positive conductor 16 through lead 31 to theauxiliary anodes 12, through the bath to the recessed sur- Todiscontinue faces 15 of the object 13 and from the prominent sur- 1faces 14 of the object through the bath to main anode 10 (now cathodic)and by way oflead 39 back to negative conductor 17.

ception, and so will not be individually described. The exceptionresides, as noted in the description referring 4 possessing theparticular features of advantage before enumerated as-desirable, -butwhich obviously is susceptible of modification in its form, proportions,detail construction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to thespecificfeatures shown, but that the means and construction herein disclosedcomprise but one of several modes of putting the inven tion into effect,

Having thus described my invention, I claim:

1. A method of electroplating irregularly shaped objects, including thesteps of immersing the object to be plated in an electrolytic bath,further inserting in the bath at least two anodes, one of said anodesconstituting an auxiliary anodeandbeing placed in a recessed area of.the object, another .of said anodes constituting the main anodeand.placed outsideof the object spaced from said auxiliary anode and withthesaid auxiliary anode being positioned between the object and saidmain-anode, connecting said anodes to a source of current on thepositive side, connecting said object to the current source on thenegative side, applying current through the circuit so established for adetermined time interval, interrupting current flow, disconnecting saidobject from the current source, reversing the electrical connection ofsaid main anode from the positive side to the negative side whilemaintaining the connection of said auxiliary anode to the positiveside,and applying current through the circuit so established for a seconddetermined time interval.

2. A method of electroplating objects presenting recesscd, hard toplate, areas, including the steps of immersing the object to be platedin an electrolytic bath, furtherinserting into the bath at least twoanodes, one of said anodes constituting an auxiliary anode and beingplaced in a recessed area of the object, another of said anodesconstituting the main anode and placed outside of the object, spacedfrom said auxiliary anode and with the said auxiliary anode beingpositioned between the object and'said main anode, and carrying out atwo-stage electroplating cycle involving a changing of polarity, in thefirst of which stages said main and auxiliary anodes are anodic whilesaid object is cathodic and in the second of which the main anode iscathodic, the auxiliary anodes are anodic and the object is bi-polar,the recessed areas being cathodic with respect to the auxiliary anodesand the more prominent parts of the object being anodic with respect tothe main anode which in the second. or reversed stage is the cathode.

3. Electroplating apparatus, including a tank to receive the object tobe plated, main and auxiliary anodes mounted in said tank, means forsuspending an object, said object to be plated in the tank, separateelectrical conductors between each of said anodes and a current sourceand between said object and said current source, and switch meanscontrolling flow through said conductors, settable to afirst position toconnect said anodes to thepositive side of thecurrent source and saidobject to Fig. 3, in the connecting of the object to the positive sideof the current source during the second stage of operation. tioned tocorrespond to contact 35 of Fig. 4. Unlike contact 35, however, which iselectrically unattached in In Fig. 5, therefore, a contact 41 is posi- 1the system, contact 41 is connected by lead 25 incorpo-1 rating resistor26 to lead 42 connected to the object 22.

Accordingly, when the switch is thrown to initiate the second stage ofoperation, object 22 is directly connected through resistor 26 to thepositive side of the. current source.

Itjis-to be noted that conventional plating can be carried out on theapparatus of the invention simply by omitting the second operationalstage. The switch 27 then functions as a simple on-off control, movingbetween neutral position and a position engaging-contacts 32 withcontacts 33 and 34.

From the above description it will't beapparent?thatofl thereis thusprovided-a deviceof the character describe'd.

to the negative side of the current source and settable to asecondposition to connect said main anode to the negative side'of thecurrent source, the auxiliary anode to the positive side and todisconnect said object from the current source.

4.- Electroplating apparatus, including a tank to re ceive the object'tobe plated, main and auxiliary electrodes mounted in said tank, means forsuspending an object, 'saidobject to be plated in the tank, separateelectrical conductors between each of said anodes and a current sourceand between said object and said current source, switch meanscontrolling flow through said conductors settable from a first positionin which said anodes are'connectcd to the, positive side of the currentsource and the object is connected to the positive side of the currentsource andthe object is connected to the negative-,side -of-the current,source to a second position in whighthe-rnain ancdeisconnected to thenegative side,

and a resistor included in the electrical connection of Number saidobject to the current source in the said second posi- 2,119,936 tion ofsaid switch means. 2,451,341

References Cited in the file of this patent 5 UNITED STATES PATENTS gg fNumber Name Date 1,526,644 Pinney Feb. 17, 1925 1,534,709 Holt Apr. 21,1925 10 1,566,265 Antisell Dec. 22, 1925 1,951,893 Winkler Mar. 20, 19346 Name Date 'te June 7, 1938 Jernstedt Oct. 12, 1948 FOREIGN PATENTSCountry Date Great Britain Sept. 15, 1930 OTHER REFERENCES The MonthlyReview, Apr. 1942, pages 301-308. Metal Finishing, Oct. 1942, pages524-526.

1. A METHOD OF ELECTROPLATING IRREGULARLY SHAPED OBJECTS, INCLUDING THESTEPS OF IMMERSING THE OBJECT TO BE PLATED IN AN ELECTROLYTIC BATH,FURTHER INSERTING IN THE BATH AT LEAST TWO ANODES, ONE OF SAID ANODESCONSTITUTING AN AUXILIARY ANODE AND BEING PLACED IN A RECESSED AREA OFTHE OBJECT, ANOTHER OF SAID ANODES CONSTITUTING THE MAIN ANODE ANDPLACED OUTSIDE OF THE OBJECT SPACED FROM SAID AUXILIARY ANODE AND WITHTHE SAID AUXILIARY ANODE BEING POSITIONED BETWEEN THE OBJECT AND SAIDMAIN ANODE, CONNECTING SAID ANODES TO A SOURCE OF CURRENT ON THEPOSITIVE SIDE, CONNECTING SAID OBJECT TO THE CURRENT ON THE ON THENEGATIVE SIDE, APPLYING CURRENT THROUGH THE CIRCUIT SO ESTABLISHED FOR ADETERMINED TIME INTERVAL, INTERRUPTING CURRENT FLOW, DICONNECTING SAIDOBJECT FROM THE CURRENT SOURCE, REVERSING THE ELECTRICAL CONNECTION OFSAID MAIN ANODE FROM THE POSITIVE SIDE TO THE NEGATIVE SIDE WHILEMAINTAINING THE CONNECTION OF SAID AUXILIARY ANODE TO THE POSITIVE SIDE,AND APPLYING CURRENT THROUGH THE CIRCUIT SO ESTABLISHED FOR A SECONDDETERMINED TIME INTERVAL.